1. Field of the Invention
The present invention relates to a wireless communication system. More particularly, the present invention relates to a switching method and apparatus for receiving Multicast Broadcast Service (MBS) data in a wireless communication system using multiple carriers.
2. Description of the Related Art
In a next generation system, i.e., a 4th Generation (4G) communication system, research and commercialization are underway to provide users with various services having a data rate of about 100 Mbps or higher. In particular, the 4 G communication system is currently being developed to ensure mobility and Quality of Service (QoS) in a Broadband Wireless Access (BWA) communication system, such as a Wireless Local Area Network (WLAN) system and a Wireless Metropolitan Area Network (WMAN) system. A representative example of such a communication system is an Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.
At present, standardization on IEEE 802.16m is ongoing as an advanced standard of the existing IEEE 802.16e. From the perspective of deployment of network equipment, a system that supports both the IEEE 802.16e and the IEEE 802.16m systems will be implemented in a transitory manner as compared to a system dedicated for IEEE 802.16m. Therefore, when an Advanced Mobile Station (AMS) moves from an IEEE 802.16e system to an IEEE 802.16e/16m combination system, a system controls the AMS to perform zone switching to a new system since it is a system having a different property from that of an existing system that supports the AMS in a corresponding zone.
FIG. 1 illustrates a zone switching scenario in a wireless communication system according to a conventional method.
Referring to FIG. 1, a mixed Base Station (BS) (or an Advanced BS (ABS)) 104 is provided that supports both an IEEE 802.16e system and an IEEE 802.16m system. An AMS 102 is provided that performs zone switching to the IEEE 802.16e system while receiving a service from the IEEE 802.16m system. Herein, a zone that supports the IEEE 802.16m system is referred to as an M zone 105, and a zone that supports the IEEE 802.16e system is referred to as an L zone 107.
In step 106, the serving ABS 104, i.e., a serving ABS of the AMS 102, sets HO_Mode=0b01 for indicating zone switching in an AAI_HandOver-CoMmanD (AAI_HO-CMD) message in the M zone 105 and then transmits the AAI_HO-CMD message to the AMS 102. In step 108, the serving ABS 104 performs synchronization with respect to the L zone 107 by using IEEE 802.16e PHYsical layer (PHY) information included in the AAI_HO-CMD message. Upon completion of the synchronization, in step 110, the AMS 102 transmits a RaNGing-REQuest (RNG-REQ) message in which a ranging purpose indication value is set to 1 to attempt re-entry to the L zone 107 of the mixed BS 104. In response thereto, the mixed BS 104 transmits a RaNGing-ReSPonse (RNG-RSP) message to report whether ranging is performed in step 112. Upon completion of the ranging process, in step 114, the AMS 102 determines whether a data path is established normally, and performs communication through the switched L zone 107.
The conventional wireless communication system performs zone switching of the AMS as described above. In order for the AMS that performs the zone switching to receive MBS data, after completion of the zone switching, Dynamic Service Addition-REQuest (DSA-REQ) and Dynamic Service Addition-ReSPonse (DSA-RSP) messages are transmitted and received through the switched zone to establish a data path for an MBS. However, a method of establishing the data path for the MBS by transmitting and receiving the DSA-REQ and DSA-RSP messages after completion of the zone switching has a disadvantage in that a time required to receive the MBS data, i.e., a delay time, is increased. Therefore, there is a need for a method of decreasing a delay time of receiving the MBS data.